Heat treatment process with oxygen enhancement of air-fuel burners

ABSTRACT

A furnace for treating metal parts includes a treatment atmosphere provided at an interior of the furnace; at least one burner operatively associated with the furnace for heating the treatment atmosphere to a temperature below a melting point of the metal parts; a passageway interconnecting the interior and the at least one burner, the passageway directing at least a portion of the heat treatment atmosphere exhausted from the furnace interior to the at least one burner for combustion; and a source of oxygen in fluid communication with the at least one burner for enriching combustion of the heat treatment atmosphere portion with oxygen at said burner. A related method is also provided.

BACKGROUND

The present embodiments relate to furnaces and processes for providingheat treatment in a protective atmosphere for metal parts andcomponents.

Known furnaces exhaust flammable atmosphere and burn-off same withoutrecovering the heat and/or gas from that exhaust. Heat and energy fromthe known processes is therefore wasted.

SUMMARY

There is therefore provided a furnace for treating metal parts,comprising a treatment atmosphere provided at an interior of thefurnace; at least one burner operatively associated with the furnace forheating the treatment atmosphere to a temperature below a melting pointof the metal parts; a passageway interconnecting the interior and the atleast one burner, the passageway directing at least a portion of theheat treatment atmosphere exhausted from the furnace interior to the atleast one burner for combustion; and a source of oxygen in fluidcommunication with the at least one burner for enriching combustion ofthe heat treatment atmosphere portion with oxygen at said burner.

There is also provided a burner for treating a furnace atmosphere formetal parts, comprising: a first inlet for fuel, a second inlet for air,a third inlet for exhaust from said furnace atmosphere, and a fourthinlet for oxygen, wherein the furnace atmosphere is at a temperaturebelow a melting point of the metal parts.

There is further provided a method for treating metal parts in afurnace, comprising providing the metal parts to a treatment atmospherein the furnace; heating the treatment atmosphere with at least oneburner to a temperature below a melting point of the metal parts;removing at least a portion of the treatment atmosphere for subsequentcombustion at the at least one burner; and enriching the subsequentcombustion with oxygen at the at least one burner.

BRIEF DESCRIPTION OF THE DRAWINGS

For a more complete understanding of the present invention, referencemay be had to the following description of exemplary embodimentsconsidered in connection with the accompanying drawing Figures, ofwhich:

FIG. 1 shows a schematic view of a gas conditioning furnace withenhancement burner embodiment of the present invention.

FIG. 2 shows a side view of a burner embodiment used in the furnaceapparatus of FIG. 1.

DETAILED DESCRIPTION OF THE INVENTION

Before explaining the inventive embodiments in detail, it is to beunderstood that the invention is not limited in its application to thedetails of construction and arrangement of parts illustrated in theaccompanying drawings, if any, since the invention is capable of otherembodiments and being practiced or carried out in various ways. Also, itis to be understood that the phraseology or terminology employed hereinis for the purpose of description and not of limitation.

In the following description, terms such as a horizontal, upright,vertical, above, below, beneath and the like, are to be used solely forthe purpose of clarity illustrating the invention and should not betaken as words of limitation. The drawings are for the purpose ofillustrating the invention and are not intended to be to scale.

Referring to FIG. 1, a furnace shown generally at 10 for heat treatmentof or providing protective atmospheres for metal parts and componentsincludes an internal chamber 12 or space and a gas generator 14, such asfor example an endothermic gas generator, mounted for coaction with thechamber 12. Furnace atmosphere 16 to be exhausted in directions 13 fromthe chamber 12 can be vented from the said chamber through an exhaustvent 18. At least one and for many applications a plurality of burners20 are mounted for operation with and heating of the furnace atmosphere16. The burners 20 may be air-fuel burners by way of example only.

Referring also to FIG. 2, a more detailed illustration of the burner 20is presented. The burner 20 includes a flange 22 or sleeve for mountingof the burner in a side wall or crown of the furnace 10. A plurality ofpassageways or conduits into the burner 20 provide alone or incombination therewith a fuel, air and oxygen (O₂) to the burner. Thatis, a first passageway or conduit 24 provides fuel to the burner 20; asecond passageway 26 provides oxygen to the burner; and a thirdpassageway 28 or conduit provides air to the burner from a blower (notshown). As shown in FIG. 2, the burner 20 may be a fuel fired direct oran indirect fired air-fuel burner and as shown, is enriched with theoxygen from the second passageway 26 or conduit. A fuel deliveredthrough the first passageway 24 may be natural gas by way of exampleonly. Other fuels can be selected from propane, liquefied petroleum gas(LPG), oil and other fuel blends.

Oxygen provided through the second passageway 26 is fed to the burner 20from a remote source 32 through a pipeline 34. The pipeline 34 mayinclude known values (not shown) or a manifold (not shown) whichinterconnects and/or transitions to the second passageway 26. The oxygensource 32 may be any of the known cylinders or on-site tanks withdelivery assemblies for the oxygen, or such source can be an oxygengeneration plant.

In operation, the burners 20 provide heating of the furnace atmosphere16 in which the parts are disposed to be subjected to the heat treatmentand/or protective atmosphere in the chamber 12. Exhaust 15 from the gasgenerator is a protective atmosphere provided or delivered to thechamber 12 to provide the protective furnace atmosphere 16, which iscirculated in the chamber 12 and thereafter recycled back to the burners20 through a passageway 17 for subsequent combustion and enhancementwith the oxygen stream provided from the second passageway 26. Theburner embodiment shown in FIG. 1 is an indirect burner, whereby exhaustfrom said burner does not actually enter the furnace atmosphere 16.

In certain embodiments, all of the furnace exhaust 17 is recirculatedback to the burner(s) 20. In certain embodiments, only a percentage ofthe exhaust 17 is recirculated to the burners 20, while a remainder ofthe exhaust is vented to the external atmosphere.

In certain embodiments, the fuel 26, furnace exhaust 17, oxygen 26 andair 28 (collectively, the “deliverables”) are mixed within the burner20. Alternatively, such deliverables to the burner 20 can be mixedupstream of the burner for combustion therein.

The burner(s) 20 also emit an exhaust 30 which can be vented toatmosphere or captured for subsequent processing.

In certain embodiments of the furnace herein, the at least one burnercomprises a fuel inlet, an air inlet, an exhaust inlet through which theheat treatment atmosphere portion is introduced to said burner, and agas inlet through which the oxygen from said source of oxygen isintroduced into said at least one burner.

In certain embodiments of the furnace the fuel, air, exhaust and gasinlets are separate from each other.

In certain embodiments of the furnace the gas inlet for said oxygen ispositioned upstream of the burner from the fuel, air and exhaust inlets.

In certain embodiments of the furnace the at least one burner isselected from the group consisting of at least one indirect firedburner, and at least one direct fired air-fuel burner.

In certain embodiments of the furnace the burner comprises a housinghaving an internal space therein and at which the first-fourth inletsare in fluid communication.

In certain embodiments of the method, the method comprises providingfuel and air to said at least one burner for the subsequent combustion.

In certain embodiments of the method said treatment atmosphere isselected from the group consisting of an annealing atmosphere, ahardening atmosphere, a carburizing atmosphere, a brazing atmosphere anda sintering atmosphere.

In certain embodiments of the method the heating is with anindirect-fired burner.

In certain embodiments of the method the enriching comprises mixing theoxygen with the portion of the treatment atmosphere.

In certain embodiments of the method the mixing is at the at least oneburner.

In certain embodiments of the method the fuel is selected from the groupconsisting of natural gas, propane, liquefied petroleum gas (LPG), oiland other fuel blends.

In certain embodiments of the method the providing comprises mixing saidoxygen, fuel and air with the treatment atmosphere portion at the atleast one burner.

The present embodiments provide for increased process efficiency of thesubject furnace, a reduction in fuel consumption of the furnace, thepotential for increased heating rate and reduced process cycle time atthe furnace, and reduced emissions from the furnace.

The present embodiments can be used in either of continuous or batchheat treatment from furnaces having flammable atmospheres such as forexample endothermic gas or similar, where carbon monoxide (CO) and/orhydrogen is present. The furnace can be heated by indirect, radiant tubeair-fuel burners. With respect to the radiant tube air-fuel burners, thefuel for same can be for example natural gas, propane or LPG.

The heat treatment processes that can occur in the subject furnaceatmosphere includes annealing, hardening, carburizing, brazing andsintering of the part or component.

A flow of the flammable atmosphere exhaust in combination with theoxygen enrichment of the burner will reduce natural gas fuel needed atthe furnace during heat treatment processes or alternatively boostheating capacity with the additional energy provided from a recycledflammable atmosphere and an oxygen enhanced combustion process. If anEndo gas furnace atmosphere is employed, the oxygen needed will be forcombustion enhancement of low heat value fuel and for increasedcombustion efficiency.

It will be understood that the embodiments described herein are merelyexemplary, and that a person skilled in the art may make variations andmodifications without departing from the spirit and scope of theinvention. All such variations and modifications are intended to beincluded within the scope of the invention as described herein and asdefined in the appended claims. It should be understood that theembodiments described above are not only in the alternative, but can becombined.

What is claimed is:
 1. A furnace for treating metal parts, comprising: atreatment atmosphere provided at an interior of the furnace; at leastone burner operatively associated with the furnace for heating thetreatment atmosphere to a temperature below a melting point of the metalparts; a passageway interconnecting the interior and the at least oneburner, the passageway directing at least a portion of the heattreatment atmosphere exhausted from the furnace interior to the at leastone burner for combustion; and a source of oxygen in fluid communicationwith the at least one burner for enriching combustion of the heattreatment atmosphere portion with oxygen at said burner.
 2. The furnaceof claim 1, wherein the at least one burner comprises a fuel inlet, anair inlet, an exhaust inlet through which the heat treatment atmosphereportion is introduced to said burner, and a gas inlet through which theoxygen from said source of oxygen is introduced into said at least oneburner.
 3. The furnace of claim 2, wherein the fuel, air, exhaust andgas inlets are separate from each other.
 4. The furnace of claim 2,wherein the gas inlet for said oxygen is positioned upstream of theburner from the fuel, air and exhaust inlets.
 5. The furnace of claim 1,wherein the at least one burner is selected from the group consisting ofat least one indirect fired burner, and at least one direct firedair-fuel burner.
 6. A burner for treating a furnace atmosphere for metalparts, comprising: a first inlet for fuel, a second inlet for air, athird inlet for exhaust from said furnace atmosphere, and a fourth inletfor oxygen, wherein the furnace atmosphere is at a temperature below amelting point of the metal parts.
 7. The burner of claim 6, furthercomprising a housing having an internal space therein and at which thefirst-fourth inlets are in fluid communication.
 8. A method for treatingmetal parts in a furnace, comprising: providing the metal parts to atreatment atmosphere in the furnace; heating the treatment atmospherewith at least one burner to a temperature below a melting point of themetal parts; removing at least a portion of the treatment atmosphere forsubsequent combustion at the at least one burner; and enriching thesubsequent combustion with oxygen at the at least one burner.
 9. Themethod of claim 8, further comprising providing fuel and air to said atleast one burner for the subsequent combustion.
 10. The method of claim8, wherein said treatment atmosphere is selected from the groupconsisting of an annealing atmosphere, a hardening atmosphere, acarburizing atmosphere, a brazing atmosphere and a sintering atmosphere.11. The method of claim 8, wherein the heating is with an indirect-firedburner.
 12. The method of claim 8, wherein the enriching comprisesmixing the oxygen with the portion of the treatment atmosphere.
 13. Themethod of claim 12, wherein the mixing is at the at least one burner.14. The method of claim 9, wherein the fuel is selected from the groupconsisting of natural gas, propane, liquefied petroleum gas (LPG), oiland other fuel blends.
 15. The method of claim 9, wherein the providingcomprises mixing said oxygen, fuel and air with the treatment atmosphereportion at the at least one burner.